1. Field of Invention
The invention relates to a process for enhancing the filling capacity of pressed tobacco, such as cut tobacco leaf or tobacco midribs, or of tobacco additional material, by treating the tobacco material with a treatment gas consisting of nitrogen and/or argon at pressures of 400 to 1,000 bar followed by a continuous decompression and subsequent thermal post-treatment of the discharged tobacco material.
2. Discussion of Prior Art
Processes of this type, which are also known as INCOM expansion processes, have to be advantageous compared with the pressure treatment of tobacco using carbon dioxide, ammonia or volatile organic gases. Thus DE 29 03 300 C2 describes such an expansion process using working pressures between 300 and 800 bar. The examples show a large effect of the final pressure on the filling capacity enhancement, but only an insignificant effect of the exposure time in the range between 1 and 10 minutes. The publication contains no reference to possible compression or compaction of the tobacco.
DE 31 19 330 C2 discloses the thermal treatment of the pressurized-gas-treated tobacco by water vapour or saturated steam and refers with respect to the high-pressure treatment to the already mentioned patent DE 29 03 300 C2.
Further, DE 34 14 625 C2 describes a cascade process, according to which, via highly varied measures such as cooling the treatment gas before charging the reactor, cooling the autoclave, or using a subcooled and liquefied treatment gas, it is to be ensured that the temperature of the discharged tobacco is below 0° C. before the heat treatment. The examples are based on filling the 200 l autoclave with 30 kg of tobacco, which corresponds to a filling density of 0.15 kg/dm3.
The patent DE 39 35 774 C2 describes the cooling of the compressed treatment gas in the autoclave via an external heat exchanger, in which case a plurality of autoclaves were connected together to form what is termed a train. The process ultimately represents a special type of cooling the gas and goods to be treated.
DE 100 06 425 C1 describes treating a tobacco of relatively low moisture up to about 16% at a working temperature above 55° C. From the autoclave volume of 2 dm3 used, and an initial tobacco weight of 300 g, a filling density of the tobacco charge of 0.15 kg/dm3 is calculated, which corresponds to the already cited DE 34 14 625 C2.
DE 100 06 424 A1 discloses the decompression having at least one holding stage and heating the system under a residual pressure to achieve tobacco discharge temperatures of 10 to 80° C.
The filling densities of approximately 0.15 kg/dm3 described in the prior art are obtained when the tobacco is charged into the pressure vessel without a further pressing operation. Increasing the filling density, in the known processes using rapid pressure buildup, produced, in contrast, lower filling capacities of the expanded tobacco material.